A contact resistance tester impedance measurement voltage and current detection circuit

Abstract

This utility model belongs to the field of detection circuit technology, and relates to a contact resistance tester impedance measurement voltage and current detection circuit. The circuit includes a voltage and current sampling circuit and a sampling data processing circuit. The voltage and current sampling circuit includes a current transformer, a load circuit, an energy metering circuit, a microcontroller circuit, an output main power circuit, and an LCD display. The energy metering circuit includes an energy metering chip. The output main power circuit includes a full-bridge inverter circuit, an output filter circuit, a current sampling circuit, and a voltage conversion circuit. This utility model can measure contact resistance at the micro-ohm level, has the advantage of high measurement accuracy, and can well characterize the tightness of connections. The use of an energy metering chip combined with a microcontroller as the core components results in extremely low procurement costs, reduces the need for external filtering design, and can accurately sample real voltage and current data.

Description

Technical Field

[0001] This utility model belongs to the field of detection circuit technology, specifically, it relates to a contact resistance tester impedance measurement voltage and current detection circuit. Background Technology

[0002] There are numerous electrical connections in the power system of a power plant. These connections have contact resistance. Under conditions such as oxidation of the contact surface, low torque of the connecting screw, and small gaps between the connection surface and the contact resistance, the contact resistance may exceed the standard. As a result, when the power is turned on, the excessive contact resistance may cause overheating and electro-corrosion due to electrical sparks, leading to equipment overheating and melting failures. Therefore, accurately measuring the contact resistance of important electrical connections is of great significance for the stable operation of the power system of a power plant.

[0003] The contact resistance measuring instrument outputs a low-voltage, high-current alternating current after the current-boosting transformer is transformed. The Kelvin connection test fixture passes the low-voltage, high-current alternating current through the electrical connection part. By measuring the voltage of the electrical connection part and the current flowing through the transformer, the accurate impedance value of the electrical connection part is obtained through the MCU (Microcontroller Unit), thereby characterizing whether the electrical connection equipment is normal.

[0004] Impedance measurement voltage and current detection principles mainly include the dedicated Kelvin measurement chip method and the acquisition of filtered voltage and current sampling data through ARM (Advanced RISC Machines) chips. The dedicated Kelvin measurement chip method has the problem of high requirements for the test environment, requiring power off and shielding against external power frequency interference during measurement. At the same time, this solution has the problem of a low upper limit of the measured impedance of the device under test due to impedance matching issues. The method of sampling and filtering through ARM chips has the problems of high requirements for the filtering circuit, large amount of sampling code, and expensive chips. The output accuracy is low, resulting in the impedance measurement accuracy not reaching the level of hundreds of microohms. Utility Model Content

[0005] To solve the above-mentioned technical problems, this utility model provides a contact resistance tester impedance measurement voltage and current detection circuit, including a voltage and current sampling circuit and a sampling data processing circuit;

[0006] The voltage and current sampling circuit includes a current transformer, a load circuit, an energy metering circuit, a microcontroller circuit, an output main power circuit, and an LCD display; the energy metering circuit includes an energy metering chip.

[0007] The input terminal of the current transformer is electrically connected to the load circuit; the output terminal of the current transformer is electrically connected to the input terminal of the energy metering chip; the output terminal of the energy metering chip is electrically connected to the input terminal of the microcontroller circuit through an optocoupler circuit.

[0008] The output terminal of the microcontroller circuit is electrically connected to the input terminal of the LCD display;

[0009] The main output power circuit includes a full-bridge inverter circuit, an output filter circuit, a current sampling circuit, and a voltage conversion circuit.

[0010] The output terminal of the microcontroller circuit is electrically connected to the input terminal of the full-bridge inverter circuit; the output terminal of the full-bridge inverter circuit is electrically connected to the input terminal of the current sampling circuit through the output filter circuit; the output terminal of the current sampling circuit is electrically connected to the input terminal of the voltage conversion circuit; and the output terminal of the voltage conversion circuit is connected to the input terminal of the microcontroller circuit.

[0011] Based on the above technical solution, the present invention can be further improved as follows.

[0012] Furthermore, the load circuit includes a load power supply and a load resistor; the load power supply and the load resistor are electrically connected; and the current transformer is connected in series with the load resistor.

[0013] Furthermore, the optocoupler circuit includes a first resistor, a second resistor, a dual-channel optocoupler, a third resistor, a fourth resistor, a first 5V DC power supply, a second 5V DC power supply, a third 5V DC power supply, and a fourth 5V DC power supply. The first 5V DC power supply is electrically connected to the first power input terminal of the dual-channel optocoupler through the first resistor. The first output terminal of the energy metering circuit is electrically connected to the first input terminal of the dual-channel optocoupler. The second 5V DC power supply is electrically connected to the second power input terminal of the dual-channel optocoupler through the second resistor. The second output terminal of the energy metering circuit is electrically connected to the second input terminal of the dual-channel optocoupler. The third 5V DC power supply is electrically connected to both the first output terminal and the third power input terminal of the dual-channel optocoupler through the third resistor. The fourth 5V DC power supply is electrically connected to the fourth power input terminal of the dual-channel optocoupler through the fourth resistor. The second output terminal of the dual-channel optocoupler is electrically connected to the input terminal of the microcontroller circuit.

[0014] Furthermore, the power metering circuit includes an RN8209 chip; the RN8209 chip contains three analog-to-digital converters connected in parallel.

[0015] Furthermore, the microcontroller chip is an STC12C5A60S2 chip.

[0016] Furthermore, the full-bridge inverter circuit includes a first DC power supply, a second DC power supply, a first diode, a fifth resistor, a sixth resistor, a first MOSFET, a second diode, a third diode, a seventh resistor, an eighth resistor, a second MOSFET, a fourth diode, a fifth diode, a ninth resistor, a tenth resistor, a third MOSFET, a sixth diode, a seventh diode, an eleventh resistor, a twelfth resistor, a fourth MOSFET, and an eighth diode.

[0017] The first output terminal of the microcontroller circuit is electrically connected to the cathode of the first diode and the first terminal of the fifth resistor; the anode of the first diode is electrically connected to the second terminal of the fifth resistor, the first terminal of the sixth resistor, and the gate of the first MOSFET; the first DC power supply is electrically connected to the drain of the first MOSFET and the cathode of the second diode; the second terminal of the sixth resistor is electrically connected to the source of the first MOSFET, the anode of the second diode, the drain of the third MOSFET, the cathode of the sixth diode, and the first output terminal of the full-bridge inverter circuit.

[0018] The second output terminal of the microcontroller circuit is electrically connected to the cathode of the third diode and the first terminal of the seventh resistor; the anode of the third diode is electrically connected to the second terminal of the seventh resistor, the first terminal of the eighth resistor, and the gate of the second MOSFET; the second DC power supply is electrically connected to the drain of the second MOSFET and the cathode of the fourth diode; the second terminal of the seventh resistor is electrically connected to the source of the fourth MOSFET, the anode of the fourth diode, the drain of the fourth MOSFET, the cathode of the eighth diode, and the second output terminal of the full-bridge inverter circuit.

[0019] The third output terminal of the microcontroller circuit is electrically connected to the cathode of the fifth diode and the first terminal of the ninth resistor; the anode of the fifth diode is electrically connected to the second terminal of the ninth resistor, the first terminal of the tenth resistor, and the gate of the third MOSFET; the second terminal of the ninth resistor is grounded to the source of the third MOSFET and the anode of the sixth diode.

[0020] The fourth output terminal of the microcontroller circuit is electrically connected to the cathode of the seventh diode and the first terminal of the eleventh resistor; the anode of the seventh diode is electrically connected to the second terminal of the eleventh resistor, the first terminal of the twelfth resistor, and the gate of the fourth MOS transistor; the second terminal of the eleventh resistor is grounded to the source of the fourth MOS transistor and the anode of the eighth diode.

[0021] Furthermore, the output filter circuit includes a first inductor, a second inductor, and a first capacitor; the first output terminal of the full-bridge inverter circuit is electrically connected to the first terminal of the first capacitor and the input terminal of the voltage conversion circuit through the first inductor; the second output terminal of the full-bridge inverter circuit is electrically connected to the second terminal of the first capacitor through the second inductor.

[0022] Furthermore, the current sampling circuit includes a Hall current sensor; the output filter circuit is electrically connected to the input terminal of the Hall current sensor; and the output terminal of the Hall current sensor is electrically connected to the input terminal of the voltage conversion circuit.

[0023] Furthermore, the voltage conversion circuit includes a third DC power supply, a second capacitor, and a first voltage divider resistor; the output terminal of the current sampling circuit is electrically connected to the output terminal of the third DC power supply, the first terminal of the voltage divider resistor, and the output terminal of the voltage conversion circuit through the second capacitor; the second terminal of the voltage divider resistor is grounded.

[0024] Furthermore, the microcontroller's input terminals are connected to several input buttons.

[0025] The beneficial effects of this utility model are: this utility model can measure contact resistance at the micro-ohm level, has the advantage of high measurement accuracy, can well characterize the tightness of the connection part, uses an energy metering chip combined with a microcontroller as the core component with extremely low procurement price, reduces external filtering design, and can accurately sample real voltage and current data. Attached Figure Description

[0026] Figure 1 A circuit diagram of an impedance measurement voltage and current detection circuit for a contact resistance tester provided in Embodiment 1 of this utility model;

[0027] Figure 2 This is the schematic diagram of the sampling circuit at the load end;

[0028] Figure 3 This is a circuit diagram of an optocoupler circuit;

[0029] Figure 4 This is the circuit diagram of a full-bridge inverter circuit;

[0030] Figure 5 This is the circuit diagram of the output filter circuit.

[0031] Icons: A - Current transformer; Z - Load resistor; U1 - Energy metering chip; U2 - Dual-channel optocoupler; U31 - First 5V DC power supply; U32 - Second 5V DC power supply; U33 - Third 5V DC power supply; U34 - Fourth 5V DC power supply; U41 - First DC power supply; U42 - Second DC power supply; U5 -; D1 - First diode; D2 - Second diode; D3 - Third diode; D4 - Fourth diode; D5 - Fifth diode; D6 - Sixth diode; D7 - Seventh diode Diode; D8 - Eighth diode; Q1 - First MOSFET; Q2 - Second MOSFET; Q3 - Third MOSFET; Q4 - Fourth MOSFET; R1 - First resistor; R2 - Second resistor; R3 - Third resistor; R4 - Fourth resistor; R5 - Fifth resistor; R6 - Sixth resistor; R7 - Seventh resistor; R8 - Eighth resistor; R9 - Ninth resistor; R10 - Tenth resistor; R11 - Eleventh resistor; R12 - Twelfth resistor; L1 - First inductor; L2 - Second inductor; C1 - First capacitor. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] As an example, see the attached document. Figure 1 As shown, in order to solve the above technical problems, this embodiment provides a contact resistance tester impedance measurement voltage and current detection circuit, including a voltage and current sampling circuit and a sampling data processing circuit;

[0034] The voltage and current sampling circuit includes a load circuit, an energy metering circuit, a microcontroller circuit, an output main power circuit, and a current transformer for the LCD display; the energy metering circuit includes an energy metering chip.

[0035] The input terminal of the current transformer is electrically connected to the load circuit; the output terminal of the current transformer is electrically connected to the input terminal of the energy metering chip; the output terminal of the energy metering chip is electrically connected to the input terminal of the microcontroller circuit through an optocoupler circuit.

[0036] The output terminal of the microcontroller circuit is electrically connected to the input terminal of the LCD display;

[0037] The main output power circuit includes a full-bridge inverter circuit, an output filter circuit, a current sampling circuit, and a voltage conversion circuit.

[0038] The output terminal of the microcontroller circuit is electrically connected to the input terminal of the full-bridge inverter circuit; the output terminal of the full-bridge inverter circuit is electrically connected to the input terminal of the current sampling circuit through the output filter circuit; the output terminal of the current sampling circuit is electrically connected to the input terminal of the voltage conversion circuit; and the output terminal of the voltage conversion circuit is connected to the input terminal of the microcontroller circuit.

[0039] The power metering chip features high measurement accuracy, serial data output, and a wide range of measurement parameters, making it suitable as the core sampling chip for impedance measurement instruments. The MCU module decodes the serial data from the power metering chip and performs internal calculations to obtain the impedance of the electrical connections, which is then output to the display screen.

[0040] A current transformer measures the current flowing through the load and converts it into an AC voltage signal, which is then sent to an energy metering chip. The energy metering chip measures the AC voltage across the load in the load circuit. The serial port of the energy metering chip is connected to an optocoupler circuit, which, after isolation and conversion, is connected to the serial port of the microcontroller circuit. The output of the microcontroller circuit is output through a full-bridge inverter circuit and an output filter circuit. The current sampling circuit collects the output signal and feeds it back to the microcontroller circuit through a voltage conversion circuit.

[0041] This detection circuit can measure contact resistance at the micro-ohm level, offering high measurement accuracy and effectively characterizing the tightness of connections. Utilizing an energy metering chip combined with a microcontroller as the core component results in extremely low procurement costs, reduces the need for external filtering, and enables accurate sampling of real voltage and current data.

[0042] Optionally, the load circuit includes a load power supply and a load resistor; the load power supply and the load resistor are electrically connected; and a current transformer is connected in series with the load resistor.

[0043] As attached Figure 2 As shown, the load power supply is input through the L and N lines of the power supply terminal. The L line represents the live wire, and the N line represents the neutral wire. The current transformer is A, and the load resistance is Z. The output terminal of the current transformer is connected to the energy metering chip U1.

[0044] Optional, as shown in the appendix Figure 3As shown, the optocoupler circuit includes a first resistor R1, a second resistor R2, a dual-channel optocoupler U2, a third resistor R3, a fourth resistor R4, a first 5V DC power supply U31, a second 5V DC power supply U32, a third 5V DC power supply U33, and a fourth 5V DC power supply U34. The first 5V DC power supply U31 is electrically connected to the first power input terminal of the dual-channel optocoupler U2 through the first resistor R1. The first output terminal of the power metering circuit is electrically connected to the first input terminal of the dual-channel optocoupler U2. The second 5V DC power supply U32 is connected to the first power input terminal of the dual-channel optocoupler U2 through the first resistor R1. The second resistor R2 is electrically connected to the second power input terminal of the dual-channel optocoupler U2; the second output terminal of the power metering circuit is electrically connected to the second input terminal of the dual-channel optocoupler U2; the third 5V DC power supply U33 is electrically connected to the first output terminal and the third power input terminal of the dual-channel optocoupler U2 through the third resistor R3; the fourth 5V DC power supply U34 is electrically connected to the fourth power input terminal of the dual-channel optocoupler U2 through the fourth resistor; and the second output terminal of the dual-channel optocoupler U2 is electrically connected to the input terminal of the microcontroller circuit.

[0045] Optionally, the power metering circuit includes an RN8209 chip; the RN8209 chip contains three analog-to-digital converters connected in parallel.

[0046] This chip is a single-phase electricity metering chip. The active power error is less than 0.1% within a dynamic range of 8000:1, and the reactive power error is also less than 0.1% within a dynamic range of 8000:1. It supports SPI / UART communication interfaces, which facilitates communication with external MCUs and data interaction with other devices.

[0047] Optionally, the microcontroller chip is the STC12C5A60S2 chip.

[0048] This microcontroller has dual serial ports, operates at a voltage of 5.5V-3.3V, and has an operating frequency range of 0-35MHz.

[0049] Optional, as shown in the appendix Figure 4 As shown, the full-bridge inverter circuit includes a first DC power supply U41, a second DC power supply U42, a first diode D1, a fifth resistor R5, a sixth resistor R6, a first MOSFET Q1, a second diode D2, a third diode D3, a seventh resistor R7, an eighth resistor R8, a second MOSFET Q2, a fourth diode D4, a fifth diode D5, a ninth resistor R9, a tenth resistor R10, a third MOSFET Q3, a sixth diode D6, a seventh diode D7, an eleventh resistor R11, a twelfth resistor R12, a fourth MOSFET Q4, and an eighth diode D8.

[0050] The first output terminal of the microcontroller circuit is electrically connected to the cathode of the first diode D1 and the first terminal of the fifth resistor R5; the anode of the first diode D1 is electrically connected to the second terminal of the fifth resistor R5, the first terminal of the sixth resistor R6, and the gate of the first MOSFET Q1; the first DC power supply U41 is electrically connected to the drain of the first MOSFET Q1 and the cathode of the second diode D2; the second terminal of the sixth resistor R6 is electrically connected to the source of the first MOSFET Q1, the anode of the second diode D2, the drain of the third MOSFET Q3, the cathode of the sixth diode D6, and the first output terminal of the full-bridge inverter circuit.

[0051] The second output terminal of the microcontroller circuit is electrically connected to the cathode of the third diode D3 and the first terminal of the seventh resistor R7; the anode of the third diode D3 is electrically connected to the second terminal of the seventh resistor R7, the first terminal of the eighth resistor R8, and the gate of the second MOSFET Q2; the second DC power supply U42 is electrically connected to the drain of the second MOSFET Q2 and the cathode of the fourth diode D4; the second terminal of the seventh resistor R7 is electrically connected to the source of the fourth MOSFET Q4, the anode of the fourth diode D4, the drain of the fourth MOSFET Q4, the cathode of the eighth diode D8, and the second output terminal of the full-bridge inverter circuit.

[0052] The third output terminal of the microcontroller circuit is electrically connected to the cathode of the fifth diode D5 and the first terminal of the ninth resistor R9; the anode of the fifth diode D5 is electrically connected to the second terminal of the ninth resistor R9, the first terminal of the tenth resistor R10, and the gate of the third MOSFET Q3; the second terminal of the ninth resistor R9 is grounded to the source of the third MOSFET Q3 and the anode of the sixth diode D6.

[0053] The fourth output terminal of the microcontroller circuit is electrically connected to the cathode of the seventh diode D7 and the first terminal of the eleventh resistor R11; the anode of the seventh diode D7 is electrically connected to the second terminal of the eleventh resistor R11, the first terminal of the twelfth resistor R12, and the gate of the fourth MOSFET Q4; the second terminal of the eleventh resistor R11 is grounded to the source of the fourth MOSFET Q4 and the anode of the eighth diode D8.

[0054] Optional, as shown in the appendix Figure 5 As shown, the output filter circuit includes a first inductor L1, a second inductor L2, and a first capacitor C1; the first output terminal of the full-bridge inverter circuit is electrically connected to the first terminal of the first capacitor C1 and the input terminal of the voltage conversion circuit through the first inductor L1; the second output terminal of the full-bridge inverter circuit is electrically connected to the second terminal of the first capacitor C1 through the second inductor L2.

[0055] Optionally, the current sampling circuit includes a Hall current sensor; an output filter circuit is electrically connected to the input terminal of the Hall current sensor; and the output terminal of the Hall current sensor is electrically connected to the input terminal of the voltage conversion circuit.

[0056] Optionally, the voltage conversion circuit includes a third DC power supply, a second capacitor, and a first voltage divider resistor; the output terminal of the current sampling circuit is electrically connected to the output terminal of the third DC power supply, the first terminal of the voltage divider resistor, and the output terminal of the voltage conversion circuit through the second capacitor; the second terminal of the voltage divider resistor is grounded.

[0057] Optionally, the microcontroller's input terminals can be connected to several input buttons.

[0058] The microcontroller can select the output SPWM (Sinusoidal Pulse Width Modulation) frequency through external input buttons, thereby achieving frequency conversion output.

[0059] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A contact resistance tester impedance measurement voltage current detection circuit, characterized by, Includes voltage and current sampling circuits and sampling data processing circuits; The voltage and current sampling circuit includes a current transformer, a load circuit, an energy metering circuit, a microcontroller circuit, an output main power circuit, and an LCD display; the energy metering circuit includes an energy metering chip. The input terminal of the current transformer is electrically connected to the load circuit; the output terminal of the current transformer is electrically connected to the input terminal of the energy metering chip; the output terminal of the energy metering chip is electrically connected to the input terminal of the microcontroller circuit through an optocoupler circuit. The output terminal of the microcontroller circuit is electrically connected to the input terminal of the LCD display; The main output power circuit includes a full-bridge inverter circuit, an output filter circuit, a current sampling circuit, and a voltage conversion circuit. The output terminal of the microcontroller circuit is electrically connected to the input terminal of the full-bridge inverter circuit; the output terminal of the full-bridge inverter circuit is electrically connected to the input terminal of the current sampling circuit through the output filter circuit; the output terminal of the current sampling circuit is electrically connected to the input terminal of the voltage conversion circuit; and the output terminal of the voltage conversion circuit is connected to the input terminal of the microcontroller circuit.

2. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The load circuit includes a load power supply and a load resistor; the load power supply and the load resistor are electrically connected; and the current transformer is connected in series with the load resistor.

3. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The optocoupler circuit includes a first resistor, a second resistor, a dual-channel optocoupler, a third resistor, a fourth resistor, a first 5V DC power supply, a second 5V DC power supply, a third 5V DC power supply, and a fourth 5V DC power supply. The first 5V DC power supply is electrically connected to the first power input terminal of the dual-channel optocoupler through the first resistor. The first output terminal of the energy metering circuit is electrically connected to the first input terminal of the dual-channel optocoupler. The second 5V DC power supply is electrically connected to the second power input terminal of the dual-channel optocoupler through the second resistor. The second output terminal of the energy metering circuit is electrically connected to the second input terminal of the dual-channel optocoupler. The third 5V DC power supply is electrically connected to both the first output terminal and the third power input terminal of the dual-channel optocoupler through the third resistor. The fourth 5V DC power supply is electrically connected to the fourth power input terminal of the dual-channel optocoupler through the fourth resistor. The second output terminal of the dual-channel optocoupler is electrically connected to the input terminal of the microcontroller circuit.

4. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The power metering circuit includes the RN8209 chip; the RN8209 chip contains three analog-to-digital converters connected in parallel.

5. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The microcontroller chip is an STC12C5A60S2 chip.

6. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The full-bridge inverter circuit includes a first DC power supply, a second DC power supply, a first diode, a fifth resistor, a sixth resistor, a first MOSFET, a second diode, a third diode, a seventh resistor, an eighth resistor, a second MOSFET, a fourth diode, a fifth diode, a ninth resistor, a tenth resistor, a third MOSFET, a sixth diode, a seventh diode, an eleventh resistor, a twelfth resistor, a fourth MOSFET, and an eighth diode. The first output terminal of the microcontroller circuit is electrically connected to the cathode of the first diode and the first terminal of the fifth resistor; the anode of the first diode is electrically connected to the second terminal of the fifth resistor, the first terminal of the sixth resistor, and the gate of the first MOSFET; the first DC power supply is electrically connected to the drain of the first MOSFET and the cathode of the second diode; the second terminal of the sixth resistor is electrically connected to the source of the first MOSFET, the anode of the second diode, the drain of the third MOSFET, the cathode of the sixth diode, and the first output terminal of the full-bridge inverter circuit. The second output terminal of the microcontroller circuit is electrically connected to the cathode of the third diode and the first terminal of the seventh resistor; the anode of the third diode is electrically connected to the second terminal of the seventh resistor, the first terminal of the eighth resistor, and the gate of the second MOSFET; the second DC power supply is electrically connected to the drain of the second MOSFET and the cathode of the fourth diode; the second terminal of the seventh resistor is electrically connected to the source of the fourth MOSFET, the anode of the fourth diode, the drain of the fourth MOSFET, the cathode of the eighth diode, and the second output terminal of the full-bridge inverter circuit. The third output terminal of the microcontroller circuit is electrically connected to the cathode of the fifth diode and the first terminal of the ninth resistor; the anode of the fifth diode is electrically connected to the second terminal of the ninth resistor, the first terminal of the tenth resistor, and the gate of the third MOSFET; the second terminal of the ninth resistor is grounded to the source of the third MOSFET and the anode of the sixth diode. The fourth output terminal of the microcontroller circuit is electrically connected to the cathode of the seventh diode and the first terminal of the eleventh resistor; the anode of the seventh diode is electrically connected to the second terminal of the eleventh resistor, the first terminal of the twelfth resistor, and the gate of the fourth MOS transistor; the second terminal of the eleventh resistor is grounded to the source of the fourth MOS transistor and the anode of the eighth diode.

7. The contact resistance tester impedance measurement voltage and current detection circuit according to claim 1, characterized in that, The output filter circuit includes a first inductor, a second inductor, and a first capacitor; the first output terminal of the full-bridge inverter circuit is electrically connected to the first terminal of the first capacitor and the input terminal of the voltage conversion circuit through the first inductor; the second output terminal of the full-bridge inverter circuit is electrically connected to the second terminal of the first capacitor through the second inductor.

8. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The current sampling circuit includes a Hall current sensor; the output filter circuit is electrically connected to the input terminal of the Hall current sensor; and the output terminal of the Hall current sensor is electrically connected to the input terminal of the voltage conversion circuit.

9. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The voltage conversion circuit includes a third DC power supply, a second capacitor, and a first voltage divider resistor; the output of the current sampling circuit is electrically connected to the output of the third DC power supply, the first end of the voltage divider resistor, and the output of the voltage conversion circuit through the second capacitor; the second end of the voltage divider resistor is grounded.

10. The impedance measurement voltage and current detection circuit of the contact resistance tester according to claim 1, wherein, The microcontroller has several input buttons connected to its input terminals.

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